Table 4—

History of type 2 diabetes and HRs of invasive breast cancer among different subgroups of the Nurses’ Health Study, 1976–1998

StratumNo diabetes
Type 2 diabetes
Breast cancer cases (n)Person-yearsBreast cancer cases (n)Person-yearsAge-adjusted HR (95% CI)*Covariate-adjusted HR (95% CI)*
BMI (kg/m2)
 <253,0501,389,2243610,5771.19 (0.86–1.66)1.23 (0.88–1.71)
 25–29.91,601613,2306719,5041.05 (0.82–1.34)1.11 (0.86–1.42)
 ≥30750302,6709929,0641.12 (0.90–1.39)1.18 (0.94–1.46)
Premenopausal1,455872,564148,2740.70 (0.41–1.19)0.83 (0.48–1.41)
 BMI <301,305772,75763,8160.66 (0.29–1.47)0.70 (0.31–1.58)
 BMI ≥3015099,80784,4580.85 (0.39–1.85)0.88 (0.40–1.96)
Postmenopausal3,3911,126,13317145,0151.13 (0.97–1.32)1.16 (0.98–1.36)
 BMI <302,862960,9998923,5641.13 (0.91–1.39)1.15 (0.93–1.43)
 BMI ≥30528164,5428221,4311.11 (0.87–1.41)1.17 (0.91–1.49)
Postmenopausal, never used postmenopausal hormones1,065379,1886416,7551.21 (0.93–1.56)1.16 (0.89–1.51)
Use of diabetes medication§
 Yes17150,7831.08 (0.93–1.27)1.15 (0.99–1.35)
 No5,4032,306,651318,4001.24 (0.87–1.76)1.21 (0.85–1.73)
Family history of breast cancer
 Yes1,079299,885408,1811.06 (0.76–1.46)1.16 (0.83–1.62)
 No4,3222,005,24016250,9641.11 (0.95–1.31)1.17 (0.99–1.37)
Ever mammogram4,3141,748,89416244,9371.08 (0.92–1.26)1.16 (0.99–1.37)
  • *

    * The reference group for calculation of each HR is the women without diabetes in the same stratum for the given covariates;

  • HR and 95% CI adjusted for age, family history of breast cancer, history of benign breast disease, height, BMI at age 18 years, current BMI, age at menarche, parity, age at first child’s birth, menopausal status, age at menopause, use of postmenopausal hormones, physical activity, and alcohol consumption;

  • information on menopausal status was not available for all participants;

  • §

    § includes insulin and sulfonylureas;

  • additionally adjusted for duration of diabetes.